1. Field of the Invention
The instant invention relates to an improved apparatus and method for forming CO.sub.2 snow within a tank provided therefor and to be contained within insulated shipping containers, railway cars, vehicle bodies and even stationary containers. The instant apparatus is somewhat more efficient than the apparatus disclosed in my co-pending U.S. application Ser. No. 702,888 in that the liquid CO.sub.2 discharged from opposing nozzles is supplied to the latter through a header pipe disposed midway between and in alignment with the opposing nozzles thereby enabling the liquid CO.sub.2 to be chilled substantially to the triple point temperature (approximately minus 69 degrees F.) immediately before the liquid CO.sub.2 under pressure is expanded by discharge from the opposing nozzles.
2. Description of Related Art
Various different forms of apparatus heretofore have been provided for forming CO.sub.2 snow within a container therefor by the discharging of liquids CO.sub.2 under pressure into such a container through conventional snow forming nozzles.
Various different forms of CO.sub.2 snow forming devices heretofore have been provided such as those disclosed in U.S. Pat. Nos. 2,475,755, 3,807,187, 4,111,362, 4,367,511, 4,381,649 and 4,462,423. However, these previously known forms of CO.sub.2 snow forming devices, for the most part, are not primarily concerned with forming the maximum amount of CO.sub.2 snow from a given quantity of liquid CO.sub.2.
Further, although my prior U.S. Pat. No. 4,381,649 discloses a means by which liquid CO.sub.2 to be discharged under pressure from snow forming nozzles is chilled to approximately the triple point temperature, the means by which this previous chilling of the liquid CO.sub.2 immediately prior to its expansion by being discharged from snow forming nozzles is cumbersome and requires the use of an eutectic solution within a tank of considerable volume.
Under substantially ideal conditions it is generally accepted that the formation of an amount of CO.sub.2 snow equivalent to 46% of the weight of liquid CO.sub.2 utilized to form that snow is the maximum amount of snow that may be formed from a given quantity of liquid CO.sub.2. Accordingly, a need exists for a means by which the forming of CO.sub.2 snow is rendered more effective so that a higher percentage in weight of CO.sub.2 snow for a given weight quantity of liquid CO.sub.2 used to form that snow may be obtained.